Humans are interesting creatures. We keep other creatures as our pets and give them human personality traits.

How else can you explain why people who have dogs as pets also dress them up in clothing to resemble little hairy malformed people creatures?

Whatever it is that makes a pet a good pet has to do with the human characteristics displayed by the pet. Cats are anti-social. Dogs are loyal. Goldfish are unobtrusive, yet colorful.

Birds are colorful, too, but cannot be considered a good bet. They smell and carry disease. At least a cat licks itself clean. Dogs lick anything. Except cats.

Hamsters and gerbils and rats don't do anything except consume and excrete and breed, perpetuating the first two, which perpetuates the latter.

Barnyard animals don't make very good pets. Goats eat anything not tied down. Pigs are, well, they're pigs. The only squeal I want to hear in my house is that of me squealing for another slice of bacon.

Why anyone would want a monkey as a pet escapes my sensibilities. Unless you already have children, in which case one more monkey won't matter that much.

The best pet is probably a well trained dog. It's loyal, relatively clean, and can be a decent burglar or fire alarm, though in some countries and cultures dogs are more of a stir fry delicacy.